NARSTO PM AssessmentChapter 5: Spatial and Temporal Pattern

Introduction and Approach

Section Contents

• Chapter Goal and Objectives

• Policy Issues on PM

•Aerosol Types: ‘Dust’, ‘Smoke’ and ‘Haze’

• General Features of North America

• Atmospheric Residence Time and Transport Distance

• Spatial-Temporal Pattern Chapter Structure

Direct questions to Rudolf B. Husar rhusar@me.wustl.edu

Chapter Goal

1. Organize the PM Assessment to address the policy issues on PM management.

2. Present new knowledge that will facilitate making better AQ management decisions.

3. State how can science be applied to reducing PM concentrations.

4. Show the linkages among AQ issues: the multi-pollutant atmosphere.

5. Need a statement on specific objectives for the Spatial-Temporal Pattern Chapter?

Policy Issues on PM

The specific Policy Issues (stated in the NAS Science-Policy Balance document)

1. Where/when are the significant PMx (PM10, PM2.5, PM1) problems, and how confident are we

2. What are the sources of PM that cause the problem

3. What are the broad approaches to fix the problem? (what pollutants; local/regional; continuous intermittent?)

4. What specific options do we have for fixing the problem?

5. What are the relationships between the PMx and other pollutant problems?

6. How can we measure progress?

7. When and how should we reassess and update our control program?

8. What atmospheric science info is needed for the review of NAQS?

Aerosol Types: ‘Dust’, ‘Smoke’ and ‘Haze’ • Aerosol are composed of multiple types. Each type may be considered a different pollutant

since it has its own class of sources, aerosol properties and associated with different effects.

• In other words, dust, smoke and haze have no more commonalities then CO, NOx and SO2 but the happen to be lumped by the current regulations.

• For this reason, the chapter will discuss the pattern of aerosol components (types) first and then the total aerosol pattern.

• The aerosol population is grouped into three types:

DUST = SOIL

SMOKE = ORGANICS + SOOT

HAZE = SULFATE + NITRATE

FMASS = DUST + SMOKE + HAZE

• These aerosol types correspond to the IMPROVE aerosol types but further aggregated for reducing complexity: The IMPROVE teps are:

SULFATE = 4.125*S Ammonium sulfate

NITRATE = 1.29*NO3 Ammonium nitrate

ORGANICS = 1.4(O1+O2+O3+O4+OP) 1.4* various organics (OMC)

SOOT = E1+E2+E3+OP Light absorbing carbon (LAC)

SOIL = 2.2AL++2.49SI+1.63CA+2.42FE+1.94TI Crustal elements

FMASS = SULFATE + NITRATE + LAC + OCM + SOIL Reconstructed fine mass

CMASS = MT-MF Coarse=PM10-FMASS

Issue: The level of aggregation needs discussion. Clearly, no matter how you aggregate it, each type has many variants in nature. I think that the IMPROVE typing (aggregation) used by Malm & Co is good and it should be retained for presenting the network results. However, I also think that DUST, SMOKE HAZE aggregation is beneficial for presenting the general aerosol pattern. I am open for discussion RBH.

Aerosol Size & Chemical Composition

• Issue: This Figure does not belong in the Spatial Temporal Pattern (STP) chapter of the NARSTO PM doc but I am offering it for consideration by the other authors.

• The figure was generated by an international group as part of the IGAC Integration and Synthesis workgroup.

• The process of figure creation can be found the here.

General Features of North America• Issue: Somewhere in NARSTO PM we could use

some general description of the continental features. Examples are here. I will be happy to help if needed. If not we can skip these. RBH

Atmospheric Residence Time and Transport Distance

• Jaenicke plot: Ultrafine 0.1 m coagulate while coarse particles above 10 m settle out more rapidly.

• PM in the 0.1-1.0 m size range has the longest residence time because they neither settle, nor coagulate.

• Froelich schem.: PM2.5 residence time increases with height. • Within the atmospheric boundary layer (the lowest 1-2 km), the residence

time is 3-5 days. • If aerosols are lifted to 1-10 km in the troposphere,(e.g. by deep

convection at fronts or convergence zones) they are transported for weeks and many thousand miles before removal.

• Atmospheric residence time and transport distance are related by the average wind speed, say 5 m/s.

• Residence time of several days yields ‘long range transport’ and more uniform spatial pattern.

• On the average, PM2.5 particles are transported 1000 or more km from the source of their precursor gases.

• The residence time determines the range of transport. For example, given a residence time of 4 days (~100 hrs) and a mean transport speed of 10 mph, the transport distance is about 1000 miles.

• The range of transport determines the ‘region of influence’ of specific sources.

Aerosol Pattern at Different Spatial and Temporal Scales

• The spatial and temporal distribution of aerosols can be described by the pattern at different scales• The pattern of ambient concentration is determined by the pattern of their causal factors: emissions,

transport and chemistry.• The spatio-temporal pattern of emissions, transport and chemistry may be different at each scale. • Temporal and spatial pattern analysis of PM data is particularly useful for source identification and

characterization.

Spatial-Temporal Pattern Chapter Structure • The main chapter grouping is by

geographic scale:– Global

– Continental/Regional

– Subregional/Local

• Within each section, the pattern are described for:

– Dust

– Smoke

– Haze

– Total (PM10, PM2.5, Bext, AOT)

Issue: Once we all make our respective contributions and see the chapter contents, it may be good to revisit the the structure for possible revisions. RHB